Follow ZDNET: Add us as a preferred source on Google.

There's one way to get accurate health data, and it doesn't involve buying a more advanced smartwatch. Surprisingly, getting better data is as simple as changing how you're wearing your smartwatch. 

Also: I walked 3,000 steps with my Apple Watch, Google Pixel, and Oura Ring - this tracker was most accurate

Accuracy is everything when it comes to health trackers. Wearables companies like Apple, Google, Oura, and Whoop have invested millions in research and development to develop sensors that can not only detect minute shifts in data but also map those details in an actionable, helpful way. 

While sensor quality improves data accuracy, sensor fit is equally important. 

How smartwatch sensors work 

To understand why a tight fit is important for smartwatch data capture, first, it's important to understand how the smartwatch sensors work. 

You may see your smartwatch glowing green around your wrist as you exercise or monitor your heart rate. That green light is actually essential in recording workout data. To continuously monitor your heart rate, a smartwatch emits green light onto your wrist. 

Red and green are complementary colors, and as your heart pumps blood during exercise, the green light absorbs the red blood. Between heartbeats, blood absorbs less green light, so more green light bounces back into the watch. 

Also: The best Apple Watch of 2026: Expert tested and reviewed

These intervals of reflection are then captured by the watch's optical sensor and converted into electrical signals. These signals are tracked and converted into per-minute heart rate measurements.  

Why does your smartwatch's tightness matter? 

The tighter your watch is to your skin, the less outside light interferes with this heart rate data capture. Exercising with a tighter watch can produce more accurate heart rate readings. 

How to correctly wear your Apple Watch 

Your Apple Watch should fit you comfortably, but it can be tighter or looser depending on the activity you're doing. For exercise and heart rate measurements, it should be comfortable but tight. Try tightening your watch before a workout for the most accurate data capture. Loosen it for everyday wear. 

Apple recommends wearing the smartwatch just above the wrist bone. It should not be on top of the wrist bone, as it's prone to shuffling around and an unsteady fit. 

Test your watch's tightness by shaking your wrist and turning your hand palm up. If you feel your watch losing contact with your wrist's skin, that's a signal to tighten your watch band.